The anatomy and physiology of blood has been of great interest to the human race for a long time, because, as recognized centuries ago, the blood system is the fluid pipeline that maintains the complex chemical balance of the human body. The blood system carries nutrients to the other living tissues of the body and at the same time carries away the waste by-products of the multitudinous complex chemical reactions that are going on inside the body and which are essential to life itself.
Severe intrusions on body tissues and/or the blood system itself often requires the supplementation of blood to the blood system. Generally, if the intrusion is not too severe or the loss of blood is not too copious, the body has a unique system for supplementing or replacing lost blood.
In those instances when the body cannot replace or supplement the needed blood because of sheer volume loss or because the body has a physiological malfunction, the replacement or supplementation can come from an external source, such as stored blood.
Historically, the storage of blood outside the body is not very old. With the onset of the Second World War, the need for large volumes of replacement blood brought on a flurry of activity in researching the best methods of storing blood.
Since the end of the Second World War and up to approximately the beginning of the present decade, the systems for storing blood that were developed were those used during the war period. At the very best, however, the duration of storage of whole blood in its liquid form, was 21 days.
Such storage systems usually involved the storage of blood in an Acid Citrate-Dextrose solution.
Recently, Dr. Lee Wood and Dr. Ernest Beutler in a publication, Transfusion, Vol. 11, No. 3, May-June, 1971, pp. 123-133, reported that blood could be stored for 35 days by the co-use of adenine with Acid Citrate-Dextrose solutions and that such a practice was the primary storage system in Sweden.
They further set forth a method they had developed for the storage of erythrocytes. They remove the plasma from whole blood and store the erythrocytes in an artificial media. Their work shows that they can get equivalent storage to the ACD-adenine storage system.
One of the major problems in the storage of whole blood is that the erythrocytes produce large quantities of lactic acid from glucose. This phenomena proceeds even when the blood is stored at low temperatures. The presence of the lactic acid, among other things, contributes to the continued decrease in the pH of the stored whole blood.
The lowering of the blood pH has a dramatic effect on the viability of the erythrocytes when the blood is transfused.
The mechanisms involved in the effect are described by Wood and Beutler in an article entitled "Preservation of Red Cell 2, 3-DPG and Viability in Bicarbonate-Containing Medium: The Effect of Blood Bag Permeability", Journal of Lab and Clinical Medicine, Vol. 80, No. 5, p.p. 723-728, "The fall in the pH of the stored cells results initially in the loss of their 2,3-diphosphoglycerate (2,3-DPG), so necessary for efficient delivery of oxygen to the tissues. Eventually, glycolysis is choked off at the pH-sensitive hexokinase and phosphofructokinase steps, so that the erythrocyte loses its capacity to live and circulate when transfused. Thus, regulation of pH plays a key role in liquid preservation".
Wood and Beutler go on to state the essential problem, "the use of very alkaline blood perservative solutions is unsatisfactory, however. Very high pH levels result in reduction of NAD to NADH in the lactate-pyrovate system, and thus impede glycolysis at the glyceraldehyde phosphate dehydrogenose step. Although alkaline preservatives result in good 2,3-DPG maintenance, adenosinetriphosphate (ATP) is rapidly depleted under these conditions, and viability is poor. To some extent, this effect may be counteracted by the addition of pyrovate to reoxidize NADH, but even very alkaline preservatives cannot absorb enough hydrogen ions to maintain the pH level above the critical values required to prevent the decomposition of 2,3-DPG.
Clearly, it would be helpful to have a highly efficient buffer system which would maintain the pH of preserved cells above 7.4 in the face of the production of large amounts of lactic acid. Yet, no buffer ion which can absorb this large amount of acid and yet be reinfused is known".
Prior art attempts at preventing degeneration of whole blood suffering from the disadvantages described above, that is, generally the buffer solutions of sufficient strength required to maintain the high pH level have the disadvantage of not being compatible enough to reinfuse in the human without deleterious side effects. Further, attempts have been made to include small pouches, containing a CO.sub.2 absorbent, inside the larger storage bag but this method is highly dependent on the ability of CO.sub.2 to penetrate the small bag to reach the absorbent and further, these small bags are readily susceptible to a mucous-like build-up on their surface which further cuts down on the transmission of CO.sub.2 to the contained absorbent.
Moreover, the small bags containing the CO.sub.2 absorbent have the possibility of highly contaminating the whole blood if they leak or are ruptured in some manner.
Further, such a bag-within-a-bag design causes complicated fabrication problems for the bag manufacturer.